As our society becomes more technologically sophisticated, electromagnetic noise pollution is becoming a growing problem. By electromagnetic noise pollution is meant unwanted electromagnetic signals, typically in the radio frequency range, which can interfere with the functioning of other electronic devices. Presently there are a great number of devices which generate electromagnetic noise pollution and a large number of devices sensitive to stray signals. For example, small DC motors are widely used in many consumer items and such motors can generate stray radio frequency signals. These signals can interfere with the operation of audio systems as well as radio controlled devices.
Motor vehicles are a prime example of the problems of electromagnetic noise pollution. Motor vehicles of present manufacture include a great number of small direct current operated motors as for example the motor powering the fuel pump. Such motors are capable of generating stray radio frequency signals. The problem is further exacerbated by the fact that audio systems in automobiles are presently more sophisticated and consumers expect high sound reproduction fidelity. These sensitive, high fidelity systems are prone to radio frequency interference from electric motors.
One solution to this problem has been to include noise reduction circuitry in the radio receivers themselves and much technology is devoted to this concept. For example, U.S. Pat. No. 3,189,824 discloses a mobile radio system having noise reduction capability.
A preferable solution is to limit the production of radio frequency noise at its source. Such noise reduction may be accomplished by various R.F. filtering or suppression circuits well-known to those of skill in the electronics arts. A typical circuit of this type includes one or more R.F. chokes which inhibit the passage of a high frequency electronic signal therethrough while allowing direct current or relatively low frequency (i.e., up to approximately 60 cycles) signals therethrough. Such device usually further include a capacitor which impedes the flow of direct or low frequency current while allowing high frequency current to pass therethrough. By appropriately disposing these particular elements, dc or low frequency energy may be supplied to a device such as a motor while short circuiting or shunting radio frequency noise emanating from that device so as to prevent it from entering the power distribution network.
The fuel pump is one critical source of radio frequency noise in an automobile and consequently various steps have been taken to include noise suppression circuitry in association therewith. While such devices have been found to function adequately in reducing noise they do introduce a new failure mode into vehicle operation. Of necessity, such radio frequency suppression circuitry includes a plurality of components affixed by soldered joints as well as a capacitor. While solder generally effects low resistance durable joints, solder joints can become a source of high resistance or open points in the circuit. Similarly, capacitors generally fail in an "open" mode wherein they become a cause of circuit failure.
When such noise reduction circuitry is incorporated in a fuel pump, failure of a single solder joint can present an open point in the power distribution circuit and effectively disable the fuel pump thereby preventing operation of the motor vehicle. Thus, a circuit intended to improve radio sound quality can produce total vehicle failure.
Obviously, it would be desirable to have a radio frequency suppression device for use in conjunction with automotive components such as a fuel pump, which device would not result in total disenablement of the fuel pump in the event of failure. The present invention provides for a radio frequency suppression device having no solder joints or capacitors disposed in series relationship in the conductive path therethrough. When used in connection with an automotive fuel pump this radio frequency suppression device provides what is called a "no walk home" feature because failure of the device merely results in the loss of radio frequency noise suppression and does not completely disable the fuel supply system for the motor vehicle. These and other features and advantages of the present invention will be readily apparent from the drawings, description and discussion which follow.